Exemplary embodiments relate to the art of semiconductor manufacturing and, more specifically, to a wafer sampling engine for a semiconductor wafer manufacturing execution system.
Semiconductor fabrication relies on multiple precise operations to produce semiconductor wafers. In order to enhance production reliability, semiconductor wafers are sampled during production. Sampling ensures that a particular tool is operating within prescribed tolerance limits. While, sampling helps engineers determine that processes are working properly, too much sampling can unnecessarily add to production time. In contrast, too little sampling, could allow a tool or tool chamber to stray from the prescribed tolerance and negatively impact production quality.
Conventional sampling engines employ three separate sampling functions. More specifically, engineers can set the sampling engine to sample either top or bottom wafers, conduct even or odd sampling, or to sample randomly. In top or bottom sampling, one or more wafers are sampled from either a top or a bottom of the lot. When set for even/odd sampling, the sampling engine samples either only even numbered wafers or odd numbered wafers. When set for random sampling, the sampling engine randomly selects wafers to be sampled. Other sampling engines utilize chamber and processing qualities to control wafer processing paths, or use monitor wafers to check tool performance. Still other sampling engines reorganize wafers in a lot based on sampling data.